This invention relates to an improved method of enhancing a population of one or more target microorganisms in the gastrointestinal tract, especially the small intestine and the large bowel of animals and humans.
It is the contention of many scientists that the health and well being of people can be positively or negatively influenced by the microorganisms which inhabit the gastrointestinal tract, and in particular the large bowel. These microorganisms through the production of toxins, metabolic by-products, short chain fatty acids, and the like affect the physiological condition of the host. The constitution and quantity of the gut microflora can be influenced by conditions or stress induced by disease, life style, travel, and other factors. If microorganisms which positively affect the health and well being of the individual can be encouraged to populate the large bowel, this should improve the physiological well being of the host.
The present inventors have realised that it would be desirable to provide a medium that would function to promote the growth and/or activity of target microorganisms in the gastrointestinal tract of animals including humans.
The present invention consists in an improved method of enhancing a population of one or more target microorganisms in the gastrointestinal tract of an animal, the improvement comprising providing to the animal a selected modified or unmodified resistant starch or mixtures thereof, such that the one or more microorganisms will selectively utilise the starch and/or increase in number and/or activity in the gastrointestinal tract.
The target population of microorganism may be enhanced throughout the gastrointestinal tract of the animal or targeted at specific sites of the gastrointestinal tract. It will be appreciated that the present invention will be suitable for any animal that requires alteration of its gastrointestinal flora. The present method is particularly suitable for use in humans.
The starches suitable include resistant or high amylose starches and modified forms thereof. The animal or human may be fed the selected resistant starch or the starch may be incorporated in a probiotic composition.
As used in this specification, xe2x80x9cresistant starchxe2x80x9d includes those forms defined as RS2, RS2, RS3 and RS4 as defined in Brown, McNaught and Moloney (1995) Food Australia 47: 272-275. Either modified or unmodified resistant starches or mixtures thereof are used in this invention. The advantage of resistant starch is that it is largely not degraded until it reaches the large bowel. Therefore it provides a readily available substrate for fermentation by the target microorganisms as soon as they arrive in the large bowel. In both cases, a preferred form of resistant starch is a high amylose starch particularly high amylose starches as disclosed and taught in WO 94/03049 and WO 94/14342, the contents of which are incorporated into this specification for the purposes of convenient cross-reference.
In WO 94/03049 and WO 94/14342, high amylose starches are disclosed which are resistant starches and include maize starch having an amylose content of 50% w/w or more, particularly 80% w/w or more, rice or wheat starch having an amylose content of 27% w/w or more and; particular granular size ranges of starches having an amylose content of 50% or more and enhanced resistant starch content, these starches including maize, barley, and legumes. This invention is not, however, limited to these forms of resistant starch. For example, other forms of resistant starch are derived from sources such as bananas and tubers such as potatoes and modified forms thereof.
It may be advantageous to also chemically modify the starch to, for instance, alter the charge density or hydrophobicity of the granule and/or granule surface to enhance the attachment compatibility between the microorganism and the resistant starch. Chemical modifications, such as etherification, esterification, acidification and the like are well known in this art as being suitable chemical treatments.
To modify the degree of enzyme susceptibility of the resistant starch the conformation or structure of the starch can be altered. Examples include acid or enzyme thinning and cross bonding using difunctional reagents.
The starches May be modified physically by, for example, crystallisation.
It is also within the scope of this invention to subject enzymatically treated resistant starches to chemical modification as described above.
As used herein, Hi-maize(trademark) (trade mark) refers to a high amylose starch obtained from Starch Australasia Limited.
In order that the present invention may be more clearly understood, preferred forms thereof will be described with reference to the following figure and examples.